Add ability to add custom variable/property into a Service Scenario

[StephenOTT]

Add ability to add a custom variable into the Configs column.

@baddlan

[baddlan]

@mario-digitalstate I added two UI fields to BPM scenarios to inject custom_data in the config property as follows:

...
"config": {
    "bpm": "camunda",
    "process_definition_key": "pothole-report",
    "custom_data": {
        "enable_custom_variables": true,
        "variable_value": {
            "aaa": "bbb"
        },
        "variable_name": "my_var"
    }
},
...

[marioprudhomme]

...
"config": {
    "bpm": "camunda",
    "process_definition_key": "pothole-report",
    "process_custom_data": {
        "enabled": true,
        "value": { // Always holds json object
            "aaa": "bbb"
        }
    },
},
...

variable name will be stored as a configuration under app.bpm.variables.scenario_custom_data, keeping the variable scope clean

type is ommitted for now to keep it simple, and assumed json. later on if we want to add types, the code will assume json if none provided, for backward compatibility.

[StephenOTT]

Notes: The variable name is controlled through a MS config.

[StephenOTT]

@mario-digitalstate in your sample, you say "Always holds json object", does that mean a json array is not supported?

[marioprudhomme]

as long as its a camunda json type compatible value, it can be anything

[StephenOTT]

okay. 👍 looks good.

[marioprudhomme]

Backend is done. Once ui has been adjusted, this issue can be closed

[baddlan]

UI updated.